Antineoplastic Combined Chemotherapy Protocols/therapeutic use; Cyclin-Dependent Kinases/antagonists & inhibitors; Leukemia, Lymphocytic, Chronic, B-Cell/drug therapy; Administration, Intravenous; Aged; Anemia/chemically induced; Antibodies, Monoclonal, Murine-Derived/administration & dosage; Antibodies, Monoclonal, Murine-Derived/adverse effects; Antibodies, Monoclonal, Murine-Derived/pharmacokinetics; Antineoplastic Combined Chemotherapy Protocols/adverse effects; Antineoplastic Combined Chemotherapy Protocols/pharmacokinetics; Area Under Curve; Asthenia/chemically induced; Bridged Bicyclo Compounds, Heterocyclic/administration & dosage; Bridged Bicyclo Compounds, Heterocyclic/adverse effects; Bridged Bicyclo Compounds, Heterocyclic/pharmacokinetics; Cyclic N-Oxides; Cyclin-Dependent Kinases/metabolism; Diarrhea/chemically induced; Drug Administration Schedule; Drug Resistance, Neoplasm; Female; Humans; Indolizines; Leukemia, Lymphocytic, Chronic, B-Cell/metabolism; Leukemia, Lymphocytic, Chronic, B-Cell/pathology; Male; Metabolic Clearance Rate; Middle Aged; Neoplasm Recurrence, Local; Pyridinium Compounds/administration & dosage; Pyridinium Compounds/adverse effects; Pyridinium Compounds/pharmacokinetics; Rituximab; Treatment Outcome